The poor you will always have with you," the new Testament teaches, but it neglects to mention that the rich can be pretty hard to avoid too. Consider the Kennedys. The family has been internationally famous since the 1930s, when F.D.R. named Joe the U.S. ambassador to Britain, and it still commands attention today, even when Joe's heirs decide not to run for office. How to account for the never failing presence of Kennedys in American life? Cynics point to an apparatus of publicists, friendly journalists and starry-eyed academics, all inspired by the family's wealth and charm and by our own...